Biomedical Engineering Reference
In-Depth Information
1
Membranes for oxygenators and plasma filters
S . B R E I T E R , Membrana GmbH, Germany
Abstract: Membranes used for blood oxygenation and blood plasma
separation represent well-proven applications as artificial organs. Although
the absolute consumption is much less compared with dialysis membranes,
their relevance for medical devices and healthcare around the world does not
hide behind the big brother. This chapter illustrates the cornerstones for
production and application of these products. Blood oxygenation membranes
produced by different methods, both symmetrical and asymmetrical, are
discussed first. The second part describes hydrophobic and hydrophilic
synthetic blood plasma separation membranes. For both types of membranes,
membrane make-up and medical device implications are considered.
Key words: blood oxygenation, plasma separation, TIPS, SIPS, membrane
structure, membrane manufacture, artificial lung, apheresis.
1.1
Introduction
Over one million patients per year undergo cardiac surgery with the aid of the
heart±lung machine. This life-saving procedure on the organ, which is said to be
the centre of life, love and desire, often takes less than an hour, although difficult
cases may extend to six or even ten hours. While the cardiac surgeon performs
the operation, a pump keeps the blood flowing and membranes inside an
oxygenator take over from the lungs in that they add oxygen and remove carbon
dioxide from the blood.
In tens of thousands of cases of sepsis or severe lung trauma, the lung needs
assistance or rest for a few days. A similar setting as for cardiac surgery may
then release the stressed organs for several days. In such cases, membrane lungs
have worked in clinics for more than four weeks.
A great number of diseases can be alleviated by removing the harmful sub-
stances from blood that cause clogging of arteries, recurring or even persisting
inflammation or overshooting immune response. Often the removal of these
substances would damage blood cells; therefore cells and blood plasma are
separated and the plasma is then cleaned vigorously. The procedure that does
this separation with the least stress for the blood cells is plasma separation with
membranes.
Over the years, tens of millions of lives have been saved and many more have
been eased with the help of membranes for blood oxygenation and plasma
